Technical references were developed in 1986 to expand on the concepts underlying technical notes. Technical references generally are lengthier than technical notes and may be produced as a collection of related documents about one subject, issued under a single BLM subject code. Although the information contained in a technical reference cannot establish policy, it can become policy through subsequent issuance as a directive, such as an instruction memorandum from the Washington Office or a BLM manual section.

For assistance accessing technical references, please contact the BLM Library at blm_library@blm.gov. Print copies of select technical references may be available for purchase; for more information, contact the BLM's Printed Materials Distribution Services (PMDS) at BLM_OC_PMDS@blm.gov or visit the PMDS website.

Since December 1982, ecological site inventory (ESI) has been the BLM’s standard vegetation inventory technique. ESI involves the use of soils information to map ecological sites and plant communities; in addition, natural resource and vegetation attributes are measured.

The purpose of Technical Reference 1734-7, Ecological Site Inventory, is to identify the procedures for completing an ESI and to describe the technique used by the Natural Resources Conservation Service (NRCS) to document and describe ecological sites. Technical Reference 1734-7 replaces previous guidance found in BLM Handbook 4410-1.

Natural resource inventories are mandated by Congress in Section 201(a) of the Federal Land Policy and Management Act (FLPMA) of 1976. Congress reaffirmed this mandate in Section 4 of the Public Rangelands Improvement Act (PRIA) of 1978; in particular, to develop and maintain an inventory of range condition and trends on public rangelands, and to keep that inventory updated on a regular basis. ESI is intended to satisfy that mandate.

The copy of Technical Reference 1734-7 linked from this page includes Information Bulletin ST-2002-106. This information bulletin describes methods for determining plot-based aboveground vegetation production and serves to clarify inconsistencies between Technical Reference 1734-7 and BLM’s National Range Handbook H-4410-1.